Question

$99$ 和 $999$ 之间有多少个整数恰好含有一个数字 $0$ ？

How many whole numbers between $99$ and $999$ contain exactly one $0?$

$72$

$90$

$144$

$162$

$180$

数字 $0$ 可以在十位或个位，这有 $2$ 种选择。

其他每一位各有 $9$ 种选择，所以共有 $2 \cdot 9 \cdot 9 = 162$ 个数。

所以正确答案是 D。

Note that the $0$ digit can either be the tens or the units digit. This gives us $2$ options for this.

There are $9$ options for each of the other digits for a total of $2 \cdot 9 \cdot 9 = 162$ numbers.

Thus, D is the correct answer.